Fish Feces Fight Climate Change

Millions of tiny fish pooping out even tinier turds may have a big impact on climate change. The fish, such as anchovies, feed on single-celled algae that live on the ocean’s surface. A study in Scientific Reports found that the fish feces sink rapidly to the bottom of the ocean, carrying with it the carbon from those algae.

Fish feces travel fast. Grace Saba of Rutgers University and Deborah Steinberg of the Virginia Institute of Marine Science found that anchovies’ dung drops approximately 2,500 feet per day.

“Pellets produced at the surface would travel the 1,600 feet to the seafloor at our study site in less than a day,” Saba said in a press release.

Each pellet of poo contained only 22 micrograms of carbon, on average.

“Twenty micrograms of carbon might not seem like much,” Steinberg said, “but when you multiply that by the high numbers of forage fish and fecal pellets that can occur within nutrient-rich coastal zones, the numbers can really add up.”

Indeed, as much as 251 milligrams of fish poop per square meter fell over the study site each day.

“Our findings show that, given the right conditions, fish fecal pellets can transport significant amounts of repackaged surface material to depth, and do so relatively quickly,” Saba said.

Fish aren’t the only marine creature unintentionally fighting climate change. On the other end of the size spectrum, the mighty sperm whale creates a conveyor belt of nutrients from the deep ocean with its dung.

When Moby Dick’s decedents dive deep and devour squid, they must return to the surface to defecate, since their excretory system shuts down during dives. The poo that the whales release on the surface feeds microorganisms, called phytoplankton. When those microorganisms die they sink and carry with them the carbon dioxide they inhaled from the atmosphere and used to construct their bodies.

"If Southern Ocean sperm whales were at their historic levels, meaning their population size before whaling, we would have an extra 2 million tonnes (2,204,623 tons) of carbon being removed from our atmosphere each and every year," lead author Trisha Lavery told Discovery News’ Jennifer Viegas.